Time delay mercury switch



July 24, 1934. c. H, LARSON TIME DELAY MERCURY SWITCH n Ennisi Filed Jan. 7, 1955 I Ela/15071,

Patented July 24, 1934.

NIT-so sTATss isemso 'mm1 pELAY MERCURY swrrcn can H. Larson, Elkhart, ina., assignor to 'she llldiake Company, a corporation of Illinois application .ianuary 7, i933, smal No. 650,656 ii claims. (c1. soo- 97) The principal object oi this invention is to provide a mercury switch capable of effecting a quick make and slow break oi an electrical circuit upon operation of thel switch' actuating 5' mechanism.

Further and other objects and advantages will become apparent as the disclosure proceeds and the/description is read in conjunction with lthe accompanying drawing, in which Fig. 1 is a vertical, sectional View of a fron contact mercury switch made in accordance with` this invention, the associated coil being shown de-energized;

Fig. 2 illustrates the position of the switch parts immediately after the coil is energized;

Fig. 3 shows the mercury covering the two tall electrodes after equilbrium has been established;

Fig. 4 shows the position of the switch parts immediately after the coil is de-energized;

Fig. 5 -is a vertical, sectional view of a back contact mercury switch madein accordance with this invention, the associated coil -being shown de-energized;

Fig. 8 illustrates the open circuit position o the switch shown in Fig. 5; and

Fig. '7 is a perspective view of the displacer.

4The following detailed description of specific embodiments of the invention is for the purpose of disclosure only and should not be construed as imposing limitations upon the appendedclaims except as required by the prior art.

Referring nrst to Figs. 1 to 4, inclusive, the mercury switch 10 comprises a glass envelope 11 into the bottom of which electrodes 12, 13 and 14 are mummy sealed. The' electrodes 1 2 and 13 project upwardly-within the envelope to substantially the same height, and are protected by insulation sleeves 15 and 16 which extend to a point slightly above the normal level of mercury 1'1.

A displacer 18, magnetically controlled, is adapted to change the level of the mercury to bridge the electrodes 12 and/or 13 with the'electrode 14.

The displacer 18 is made of suitable magnetic material, such as iron, or magnetic material combined with some othermaterial having desirable characteristics For example, the lower part oi."

tudinal groove 22 cut into the side of the displacer accommodates'the electrode 12 and thereby makes possible -a smaller switch envelope. Tests have shown that the groove has a tendency to .minimize eddy currents when the switch is operated on alternating current and the eiciency of the switch is correspondingly increased.

Springs 23 and 24 cushion the displacer from the ends of the envelope andprotect the envelope from breakage due to rough handling inAshipment, or excessive magnetic forces.

After the electrodes 12, 13 and 14 have been sealed into the bottom of the envelope 11 and the charge of mercury 17 and displacer. 18 have been placed in the envelope, a vacuum pump is attached to the open end to drawout all air within the envelope and replace it with a suitable gas illl `such as helium, hydrogen, nitrogen, or the like. y

The envelope is then sealed oi! at 25.4

The switch actuating mechanism comprises a coil 26 wound upon a spool 27 havinga central aperture 28 adapted to receive circular pole sleeves 29 and 30.Y The pole sleeves are madeof'magnetic material and with the iron yoke 31, which is preferably laminated, form a magnetic circuit which is'complete except for the air gap 32. When the coil 26 is energized, the displacer 18 is drawn downwardly in its eifort to'close the air gap and mercury is, consequently displaced.

The electrodes 12 and 13 are intended to b'e connected by a common lead 33 which may be connected to one side of the battery 34 or other source f electrical energy. The electrode 14 may be connected through a loadv35 to the other side loi' the battery. This simple circuit is suflicient to show the manner in which the switch may be used.`

The switch' shown in Fig, l is termed a front 100 contact switch because the electrical circuit through the electrodesy is heldv open as long as the coil 26 is de-energized. As soon as the coil is energized, the displacer 18 is immediately lowered and the mercury level on the outside of the 105 displacer rises to the position shown in Fig. 2. The bared portion of the electrode 12 thus comes in contact with the mercury and the electricalA circuit through the electrodes 12 and 14 is at once completed. 11G

Although the electrode 12 is immediately placed in contact with the mercury by the lowering of the plunger, the electrode 13 is not covered with mercury until the gas which'is trapped within the plunger has had an opportunity to escape through the porous thimble 20. When the pressures" on the inside and outside of the displacer have been equalized after a.' given time interval,

the mercury takes the position shown in Fig. 3.

the load remains unbroken until suiiicient gasv has been admitted to the interior of the displacer 18 through the porous wall 20 to permit the mercury column within the displacer to fall to its normal level. Consequently, the breaking of the electrical circuit is timed according to the rate at which the gas is allowed to enterthe displacer.

From the above, it is clear that the switch eects aquick make and slow break of the electrical circuit. The time interval for the breaking of the electrical circuit may begoverned by the slection of suitable material for the porous thimble l20, the particular gas iill, the ,height of the electrodes, the mercury illl, and other variables.

It will be understood that any suitable restricted 3s i passageway in the top of the displacer 18 will produce alike result, and this invention is not limited to the use of a porous material for the gas relief vent.

In Figs. 5 and 6, there is illustrated a modifica- 46. tion oi' the invention, in which the switch is of the back contact type. In other words, the electrical circuit through the electrodes is closed when the associated coil is de-energized, and opened when the coil is energized. To accomplish this, the`air 43' gap 36 in the magnetic circuit is placed adjacent tothe top of the envelope and the displacer 37 is of somewhat heavier construction to compen- 4sate for the difference in the forces oi gravity and buoyancy. The operation of the switch, however, is virtually the same as the front contact switch shown in Figs. 1-4 inclusive, the only diii'erence being that Lmagnetic force is used for lifting the displacer (instead of buoyancy, asin Fig. 4,) and,

g gravity is relied upon for lowering the displacer 58. (instead of the magnetic force used in-Fig. 2) What I claim, therefore, is: y l. In a mercury switch adapted to eect a quick make and slow break of an electrical circuit, the combination of a switch envelope, spaced elecoi) trodes in the envelope, two of which are connected to a common lead, a charge oi' mercury in the envelope adapted to make or break an electrical circuit, according to its level, between said two lelectrodes and another electrode. a displacerfor changing the mercury level, said displacer being telescoped over one of said two electrodes and being equipped with .means for slowly equalizing tllie pressures on the inside and outside of the disp acer.

make and slow break of an-e1ectrlcal circuit, a vertical switch envelope, a charge of mercury in the envelope; a magneticallycontrolled displacer for changing the mercury level, spaced electrodes '75- in the envelope adapted to be bridged by the mer- `to the changes of the mercury level.

2. In a mercury switch adapted to effect a quick cury for completing an electrical circuit, one oi' said electrodes projecting into the displacer, a gas relief vent in the displacer, and an auxiliary electrode on the outside of the displacer subject 3. In a mercury switch of the class described, a vertical switch envelope, a mercury illl, a plurality of spaced electrodes in the envelope, two of which are substantially the same height and are adapted to be connected to a common lead, a displacer telescoped over one of said two electrodes, a restricted gas passage in the upper part of the displacer, and means for actuating the displacer to change the mercury level.

4. In a mercury switch of the class described, a vertical switch envelope, spaced electrodes in the envelope, a charge of mercury adapted to make or break an electrical circuit through the electrodes according to its level, a displacer telescoped over one oi.' the electrodes for displacing the mercury, a restricted gas passage in the displacer, and an auxiliary electrode on the outside of the displacer also subject to the changeof mercury level and adapted to be connected by a common lead to the electrode within the displacer.

5. In a mercury switch adapted to eiiect a quick make and slow break of an electrical circuit, the combination of a switch envelope, spaced electrodes in the envelope, a mercury iill, a displacer telescoped over one of :the electrodes, adapted to make or break an electrical circuit through the electrodes by displacing the mercury and changing its level, a gas relief vent in the displacer, and an auxiliary electrode on the outside of the displacer subject to the change in the mercury level and connected to the electrode within the displacer.

6. .In a mercury switch adapted to effect a quick make and slow break of an electrical circult, the combination of a switch envelope, spaced 115 'electrodes in the envelope, a mercury ll, a displacer telescoped over one of the electrodes,

, to changes in the mercury level and connected to the electrode within the displacer. L

I. In a mercury switch adapted to eil'ect a 125 quick make and slow break of an electrical circuit, `a vertical switch envelope, a plurality of electrodes lsealed through the bottom of the envelope and projecting upwardly, two of said electrodes being substantially the same' height and 130 being provided with insulating sleeves to a point adjacent their tops, a charge of mercury in Ithe envelope adapted to make or break an electrical circuit between said two electrodes and a third electrode according to the mercury level, a displacer telescoped over one of -said two electrodes for changing the mercury level, and a gas relief vent in the displacer;

8. In a mercury switch adapted to eilect a quick' make and slow break of an electrical cir- 140 cuit, a verticaljswitch envelope, a charge of mercury in the envelope, a magnetically controlled displacer for changing the mercury level, spaced electrodes in the envelope adapted to be bridged by the mercury for completing an electrical circuit,- two being adapted to be connected to the same side of the circuit and a third to the other side, one of said two first-mentioned electrodes having a time delay element associated therewith and the other of said two electrodes beingimmediately responsive tothe displacing actionot the 9. In a mercury switch adapted to effect a quick make and slow break of an electrical circuit. a vertical switch envelope, a charge of mercury in the envelope, a magnetically controlled displacer for changing the mercury level, spaced electrodes in the envelope adapted to be bridged by the mercury for completing an electrical circuit,means for delaying the movement o! mercury away from one of the electrodes when the displacer is shifted from its lowered position to its raised' position, and an auxiliary electrode adapted to be connected to said one electrode and immediately responsive to the displacement action of the displacer.

10. In a mercury switch adapted to etlfect a quick make and slow break of an electrical circuit, a vertical switch envelope, a charge of mercury in the envelope, a magnetically controlled displacer for changing the mercury level, spaced electrodesin the envelope adapted to be bridged by the mercury for completing an electrical circuit, means for delaying the movement of mercury away from one of the electrodes when the displacer is shifted from its lowered position to its raised position, and an auxiliary electrode re sponsive immediately to the displacement action of the displacer.

1l. In a mercury switch, a switch envelope, spaced electrodes in the envelope, a gas nll-,a quantity of mercury in the envelope adapted to be manipulated to make or break an electrical circuit through the electrodes, a. hollow body telescoped over one'ofthe electrodes and presenting a relatively large opening to the mercury and a relatively small opening to the gas. and an auxiliary electrode adapted to be connected to the one over which the hollow body is telescoped, said auxiliary electrodeA being responsive to changes in the mercury level outside of the displacer.

, CARL H. LARSON. 

